In recent years, the scale of software mounted in an electric control device (electric control unit (ECU)) for vehicles increases in accordance with progresses of a driving support function and automatic driving technologies. Accordingly, the number of times of recall due to inconvenience of software and the scale of the number of vehicles that are necessary to respond to one time of recall increase. In addition, in accordance with progresses of communication networks, signs of wide use of connected cars enabling automatic vehicles to be wirelessly connected to a center system or the like are shown. In such situations, there are increasing requests for vehicle-dedicated remote software updating technologies for remotely updating ECU software of vehicles by applying a wireless remote software updating technology conventionally used in cellular phones and television sets to the vehicles.
Relating to the remote software updating technologies described above, for example, in PTL 1, for example, an over the air (OTA) technology used for updating a program of a mobile terminal through a difference update has been disclosed in PTL1. In the technology disclosed in PTL 1, differences between programs before and after an update are downloaded into a reception device and are stored in a memory together with the program before the update, and the program of the reception device is updated using such information.